1. Field of the Invention
The present invention relates to a load control device for controlling the amount of power delivered from an alternating-current (AC) power source to an electrical load, and more particularly, to a smart lighting control device having a rotary intensity adjustment actuator, such as a rotary knob or a rotary wheel, for control of the intensity of a connected lighting load.
2. Description of the Related Art
A conventional wall-mounted load control device is mounted to a standard electrical wallbox and is coupled between an alternating-current (AC) power source (typically 50 or 60 Hz line voltage AC mains) and an electrical load. Standard load control devices, such as dimmers and motor speed controls, use a bidirectional semiconductor switch, such as a triac, or one or more field effect transistors (FETs), to control the current delivered to the load, and thus, the intensity of the lighting load or the speed of the motor. Dimmers have a line terminal (or hot terminal) coupled to the AC power source and a load terminal (e.g., a dimmed hot or a switched hot terminal) coupled to the electrical load, such that the semiconductor switch is coupled in series between the source and the electrical load. Using a phase-control dimming technique, the dimmer renders the semiconductor switch conductive for a portion of each line half-cycle and renders the semiconductor switch non-conductive for the other portion of the line half-cycle to selectively provide power to the load.
A typical dimmer also has a mechanical switch coupled in series with the semiconductor switch to disconnect the electrical load from the AC power source to turn the electrical load on and off. An actuator provided at the user interface of the wall-mounted dimmer allows a user to actuate the mechanical switch to toggle the load on and off. The dimmer often comprises an intensity adjustment actuator to allow the user to adjust the amount of power being delivered to the load. For example, a prior art rotary dimmer comprises a rotary knob for adjusting a rotary potentiometer inside the dimmer to adjust the intensity of a connected lighting load. The rotary knob of the rotary dimmer may also be pressed in to actuate a mechanical switch in the dimmer to turn the lighting load on and off.
Some load control devices, such as “smart” two-wire dimmers, include a microprocessor or other processing means for providing an advanced set of control features and feedback options to the end user. The advanced features of a smart dimmer may include, for example, a protected or locked lighting preset, fading, and double-tap to full intensity. To power the microprocessor, smart two-wire dimmers include power supplies, which draw a small amount of current through the lighting load each half-cycle when the semiconductor switch is non-conductive. The power supply typically uses this small amount of current to charge a storage capacitor and develop a direct-current (DC) voltage to power the microprocessor. An example of a smart dimmer is disclosed in commonly assigned U.S. Pat. No. 5,248,919, issued on Sep. 28, 1993, entitled LIGHTING CONTROL DEVICE, which is herein incorporated by reference in its entirety.
Smart dimmers have also been included as part of multi-location lighting control systems, such as, for example, a radio-frequency (RF) lighting control system. Such lighting control systems have included main dimmers wired directly to controller lighting loads, and remote control devices (such as keypads or remote dimmers). Each of the main dimmers and remote dimmers of the prior art multi-location lighting control systems typically comprise, for example, a rocker switch, rather than a rotary knob or a slider control, for adjustment of the intensity of the locally-controlled or remotely-controlled lighting loads. Each of the main and remote dimmers may also comprise one or more visual indicators, e.g., light-emitting diodes (LEDs), to provide feedback of the intensity of the controlled lighting load to the user. However, user interfaces of such dimmers are not always easy to understand and use for a novice user of the multi-location lighting control system.
Thus, there is a need for a smart load control device that has a simple, intuitive user interface (for example, including a rotary knob) and is able to be included as part of a multi-location load control system.